In traditional configurations, Virtual SAN requires 3 hosts, with at least one disk group each, configured in a vSphere Cluster with Virtual SAN enabled, with a VMkernel port configured for Virtual SAN traffic that has connectivity to other hosts in the cluster. Note* Multicast traffic is required.

More detailed information for the different versions of Virtual SAN can be found in the relative KB article for each version of Virtual SAN.

What type of hardware is required for Virtual SAN?

Hosts that are certified to run VMware vSphere along with components that are certified to run Virtual SAN. Components certified for Virtual SAN are tested by the VMware Storage and Availability Business Unit.

Virtual SAN can be installed on hardware in a bring your own component, Ready Node, or Engineered Appliance offering.

Bring Your Own
The VMware vSphere Hardware Compatibility List details which hosts and CPU configurations are supported with ESXi.
The vSphere HCL can be found here: http://vmwa.re/hcl

When combined with the vSphere HCL, the Virtual SAN Compatibility Guide provides a list of hardware certified to run Virtual SAN.
The Virtual SAN Component HCL can be found here: http://vmwa.re/vsanhclc/

Warning: Using uncertified hardware may lead to performance issues and/or data loss. The reason for this is that the behavior of uncertified hardware cannot be predicted. VMware cannot provide support for environments running on uncertified hardware.

What are the cluster requirements of Virtual SAN?

Cluster requirements include

A minimum of 3 nodes must contribute storage, unless using a 2 Node configuration along with an external witness.

2 Node configurations were introduced in Virtual SAN 6.1.

All ESXi hosts must be managed by vCenter Server 6.0 and configured as a Virtual SAN cluster member.

vCenter Server must be at a release level equal to or higher than the ESXi hosts it is managing.

ESXi hosts in a VSAN cluster may not participate in any other cluster.

What are the memory requirements of Virtual SAN 6?

Memory requirements are determined by the number of disk groups and devices that are managed by ESXi.

Hosts should contain at least 32GB of RAM to accommodate the maximum number of disk groups and devices.

BaseConsumption: This is the fixed amount of memory consumed by Virtual SAN per ESXi host. This is currently 3 GB.

This memory is mostly used to house the VSAN directory, per host metadata, and memory caches.

NumDiskGroups: This is the number of disk groups in the host, should range from 1 to 5.

DiskGroupBaseConsumption: This is the fixed amount of memory consumed by each individual disk group in the host. This is currently 500 MB. This is mainly used to allocate resources used to support inflight operations on a per disk group level.

SSDMemOverheadPerGB: This is the fixed amount of memory we allocate for each GB of SSD capacity.

This is currently 2 MB in hybrid systems and is 7 MB for all flash systems.

Most of this memory is used for keeping track of blocks in the SSD used for write buffer and read cache.

What are the processor requirements?

Processors that are approved on the vSphere Compatibility Guide are approved for use with Virtual SAN.

Virtual SAN typically consumes no more than 10% of CPU overhead per host for versions up to 6.1.

When using advanced Space Efficiency features in All-Flash architectures of Virtual SAN 6.2, may consume an additional 5% of CPU.

What are the software requirements?

The software requirements for Virtual SAN 6 are:

VMware vCenter Server must be at the same version or higher than the ESXi hosts it is managing.

ESXi hosts that participate in Virtual SAN Clusters must be version 6.0.

ESXi hosts participating in a VSAN 6.0 cluster must be running the same ESXi version.

Hosts versions may be mismatched during the duration of an upgrade.

When upgrading from Virtual SAN 5.5 to 6.0, the on-disk format must be upgraded to use all available features for the specific edition of Virtual SAN.

The VSAN-FS format for Virtual SAN 6.0 and 6.1 must be 2.0 to use all features of each edition.

The VSAN-FS format for Virtual SAN 6.2 must be 3.0 to use all features of 6.2.

What are the network requirements?

The networking requirements for Virtual SAN 6 are:

For hybrid configurations, each host must have a minimum of a single physical 1 GB Ethernet NIC available solely for Virtual SAN use.

For all flash configurations, each host must have a minimum of a single physical 10 GB Ethernet NIC available for Virtual SAN use. This NIC can be shared with other traffic.

Layer 2 multicast must be enabled on the physical switch connecting all hosts in the VSAN cluster. Layer 3 multicast is supported.

Each ESXi host in the cluster must have a vmkernel port, regardless of whether it contributes to storage. For more information, see the Set Up a VMkernel Network for Virtual SAN section in the VMware Virtual SAN 6.0 Documentation.

Note: When running multiple Virtual SAN clusters, it is required to have isolated Virtual SAN networks.
This isolation can be achieved through the use of:

Each Virtual SAN network residing on a non-routed VLAN

Each Virtual SAN network with its own distinct Multicast addressesKB Article 2075451 covers setting Multicast addressing in Virtual SAN.